According to the pilot, he was practicing an engine out maneuver to a landing on the water. At 500 feet mean sea level, the pilot "cut" the engine power and turned the carburetor heat to full on. The pilot stated that as he neared the water, he started to flare when the left float grabbed the water first. According to the airplane owner/witness, the pilot made his approach too fast and too flat. The airplane impacted the water with the front right section of the landing float and the airplane cart-wheeled to the right.Post-accident examination of the airplane revealed that both wings and the fuselage incurred substantial damage due to impact with the water. The pilot reported no pre-impact mechanical malfunctions or failures with the airplane that would have precluded normal operation.